1. Field of the Invention
The present invention relates to a method for controlling the fuel supply of an internal combustion engine.
2. Description of the Prior Art
There are fuel injection types for injecting and supplying the fuel into an internal combustion engine of automobiles or the like by an injector. Among these types, there is a type in which: a pressure in the intake air passage downstream of the throttle valve of the intake air system and an engine rotating speed are detected; a basic fuel injection time duration T.sub.i is determined at the period synchronized with the engine rotating speed in accordance with the result of detection; further, an increase or decrease correcting coefficient is multiplied to the basic fuel injection time duration T.sub.i in accordance with other engine operation parameters such as an engine coolant temperature or the like, or with a transient change of the engine; and thereby determining a fuel injection time duration T.sub.out corresponding to the amount of the required fuel injection.
In such a fuel supply control method, there is a time lag in the control operation from the detection of the pressure in the intake air passage until the fuel is actually injected. When the pressure in the intake air passage varies as in the acceleration or deceleration of the engine, the pressures in the intake air passage when it is detected and when the fuel is injected differ. Therefore, the pressure in the intake air passage upon fuel injection is presumed on the basis of the change in the pressure in the intake air passage detected already. Then, the basic fuel injection time duration is determined using this presumptive value.
On the other hand, fuel adheres to the wall surfaces of the intake air manifold during operation of the engine and its amount of deposition differs depending on the operating state. Practically speaking, in the decelerating operation of the engine, an absolute pressure in the intake manifold is lower than that in the accelerating operation and the fuel deposited onto the wall surface in the intake manifold is drawn into the engine, so that the time duration until the deposition amount becomes stable becomes long. Therefore, for improvement in operation state, it is desirable to add a correction value regarding the fuel adhered onto the wall surface in the intake manifold to the presumptive value of the pressure in the intake air passage in the case where this pressure varies.